When everything just fits together, we often don't notice it. What happens depends on too many factors for people to truly understand, so much of work is an attempt to get it all in order. This is where ritual plays a key role, the idea that we are a part of something, to play a role whether we like it or not. Some of us choose to live without beleif at all. To get ourselves involved in something without knowing, we have an aversion. We have, therefore, an idea of the Devil without really knowing that we have one at all.
This is all pure lunacy. Either you are in a world that contains both aspects true and false, or you do not exist on this plane at all. And every dimension contains this binding of shadows, this liberation of light. There are those who would like to pick and choose. There are those who would like to seperate, to decide for others what is true. Some of this has already been covered. But that is the point, that everything has many sides and exists both before and after it appears.